It's one thing to have a future Generation Pokemon in a current Generation movie. It's also true with the reverse, an older Generation Pokemon having a slightly/partial role in a current/future Generation. That isn't the problem. It's a completely different story when the future Generation Pokemon is the Starting Pokemon. They've never debuted Starting Pokemon in an earlier Generation movie. How come we never saw Turtwig, Chimchar, or Piplup from Destiny Deoxys to Prince of the Sea Manaphy? They aren't going to promote the starters since they will just get that treatment in the first episode of the new saga, when Ash and/or his companions get them, and then in that new series' movies, like Chimchar did in The Rise of Darkrai.